<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>气泡框效果</title>
    <style>
        div.pao{
            width: 0;
            height: 0;
            border: 10px solid;
            border-color: transparent transparent red transparent;
        }
        div.pao::after{
            content: '';
            width: 0;
            height: 0;
            border: 10px solid;
            position: absolute;
            bottom: 450px;
            left: 9px;
            border-color: transparent transparent blue transparent;
        }
        div.content{
            border: 2px solid red;
            width: 100px;
            height: 50px;
            position: relative;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="pao"></div>
        <div class="content"></div>
    </div>
</body>
</html>